Analysts have suggested that Khodorkovsky was singled out by Mr Putin when he came to power in 2000 as president and set about breaking the hold of the much-loathed oligarchs who had flourished under his predecessor, Boris Yeltsin.

Supporters of Khodorkovsky, 50, seek to portray him as the victim of a gross miscarriage of justice.

Komsomol years

Khodorkovsky had made his fortune - estimated by Forbes magazine to be more than $15bn (£9.72bn) - from the controversial privatisation of Soviet state assets.

A native of Moscow and the son of two engineers, he had studied at Mendeleyev Chemistry Institute and began his career as a loyal Soviet-era Communist Party member, running a computer import business under the wing of the party's youth movement (Komsomol) in the 1980s.

Khodorkovsky's downfall rocked Russia

In 1987 - four years before the fall of the USSR - he founded what would become Menatep, one of post-Soviet Russia's first private banks.

He made his first millions in the 1990s when the bank acquired massive amounts of shares in companies that were privatised for bargain prices.

Fertiliser firm Apatit was bought in 1994, later becoming the focus of the initial trial against Khodorkovsky and his business partner, Platon Lebedev.

His business empire, prosecutors later claimed, was little short of a gangster operation and Apatit shares were alleged to have been picked up illegally via the use of umbrella companies.

In 1995, Khodorkovsky acquired Yukos at a state auction at the knockdown price of $350m.

It had come close to folding but now Yukos became Russia's second biggest oil company, pumping one in every five barrels the country produced.

It began publishing its accounts to international standards and was soon seen as one of Russia's most transparent, well-run companies with international investors clamouring to own shares.

Khodorkovsky even served as deputy fuel and oil minister during Yeltsin's presidency.

Arrest

He was first arrested in October 2003 on charges of tax evasion, fraud and embezzlement.

Mikhail Khodorkovsky Timeline

1963 - Born in Moscow, son of chemical engineers

1981 - Enters Mendeleyev Chemistry Institute, Moscow

1980s - Sets up computer software business with fellow students

1987 - Founds Menatep bank

1994 - Buys Apatit fertiliser company at auction

1995 - Buys Yukos for $350m, with Menatep assuming $2bn in debt

2003 - Arrested for tax evasion, embezzlement and fraud

2004 - First court case begins

2005 - Found guilty on six of seven charges, jailed for eight years

2007 - Yukos declared bankrupt

March 2009 - Second court case starts in Moscow

December 2010 - Convicted of embezzlement and money laundering

August 2013 - second sentence reduced

December 2013 - President Putin pardons him after a request for clemency and he is flown to Germany

Jailed in 2005 for eight years, he was tried again two years before his release date on further charges of embezzlement and money laundering. He is due for release in August 2014.

His lawyers maintained the charges against him were trumped up, carried out on the orders of senior figures in the Kremlin who objected when his activities strayed into the political arena.

Khodorkovsky had provided funding to nearly all political parties, including the communists, and acquired the rights to publish the prestigious Moskovskiye Novosti newspaper. He also hired a well-known investigative journalist critical of Vladimir Putin.

He had made no secret of his support for the liberal opposition to Mr Putin.

When asked about Khodorkovsky on live television before the second trial verdict was read out, Mr Putin said simply, "a thief should be in jail".

'Hard to stay strong'

Yukos filed for bankruptcy in 2006 while Khodorkovsky was serving his first sentence at a Soviet-era labour camp in the Chita region of eastern Siberia, 4,700km (3,000 miles) east of Moscow.

Khodorkovsky is seen here in court in Moscow in June 2011

He was moved in 2011 to a prison camp in Karelia, near the Finnish border.

In August, when his prison sentence was reduced and an early release date was set for 2013, he continued to insist that the cases against him had been fabricated.

In an address to the court by video link, he argued that the judiciary was being manipulated by politicians.

"Whether we are talking about elections or business affairs or even mutual relations in matters of faith, the words 'a criminal case has been initiated' are key," he said.

In an interview for BBC News earlier this year, Khodorkovsky's mother Marina said: "Because our courts are unfair, it is hard to stay strong. But people need to be honest, tell the truth and speak out. They should not be afraid."